A number of reports have already been made on the process for producing olefin polymers using a metallocene complex. For example, JP-A-58-19309 discloses a process for producing olefin polymers which uses a metallocene complex and an aluminoxane. The process has a problem in that when olein is polymerized with the disclosed catalyst which uses bis(cyclopentadienyl)zirconium dichloride and methylaluminoxane, the molecular weight of the olefin polymer obtained is low.
The specification of WO87/02370 discloses that the above-mentioned problem is improved by a transition metal complex having a ligand comprising two phenoxy groups linked each other by a sulfur atom. However, the system disclosed in WO87/02370 which uses 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride and methylaluminoxane and also a system disclosed in JP-A-5-230133 which uses 2,2'-thiobis(6-tert-butyl-4-methylphenoxy)titanium dichloride, triisobutylaluminum and triphenylmethane tetrakis(pentafluorophenyl)borate involve a problem in that the catalytic activity is unsatisfactorily low from the industrial point of view although the molecular weight of the polymer produced is improved.
JP-A-3-163088 discloses a transition metal complex which has a ligand comprising a cyclopentadienyl ring and an amino group linked thereto by a silicon atom, namely, (tert-butyl-amido)dimethyl(tetramethylcyclopentadienyl)silane zirconium dichloride.
However, no transition metal complex has yet been known which has a ligand comprising a cyclopentadienyl ring and an aromatic ring having oxygen atom in the substituent linked with each other by a sulfur atom or a phosphorus atom.
In recognition of the situation, the objects of the present invention are to provide a transition metal complex useful in industrial process as an olefin polymerization catalyst component which has a ligand comprising an aromatic ring having a hetero atom in the substituent and a cyclopentadienyl ring linked with each other by a hetero atom and to provide a highly active olefin polymerization catalyst and a process for producing olefin polymers.